Displaying items by tag: Embryo Development in Balanoglossus

Asexual Reproduction: Gilchrist described asexual reproduction in Balanoglossus capsensis. In the summer season its posterior end will divide into a number of bits. Each bit will develop into a new individual.

Sexual Reproduction: Sexes are separate, sexual dimorphism is absent. The gonads are simple. They are present in one or many rows in the branchio-genital region.

Each gonad will give gonoduct. This gonoduct will open out through a pore externally. In male the gonads are called testes. They produce sperms. In female the gonads are called ovaries. They produce ova. They are liberated into water. Fertilization will take place in water. It is called external fertilization.

The fertilized zygote will undergo holoblastic clevage.

In Balanoglossus kowaiowsley the development is direct. No larval form is seen in its life history.

In other species of Balanoglossus a larval form called 'Tonaria" is seen in the development. It Will undergo metamorphosis and becomes adult.

It shows distinct digestive tract. It opens with mouth on the ventral side. At the posterior end it opens out through anus. This tract is curved.

It will swim with the help of cilia. a) Pre oral band of cilia is significant one. It surrounds the mouth and then it transforms as post oral band of cilia. b) Around anus a band of cilia is present called anal ciliated band.

Tornaria takes micro-organisms of sea water as food.

It shows two eye spots and nerve cells.

It can notice the light intensity with the help of eye spots.

This larva after leading a free swimming lobe for some time it will transform into adult. It is called metamorphosis.

Metamorphosis:

Eye spots and ciliated bands will slowly reduce.

By the development of two constrictions in the body, it is divisible into 3 parts. a.anterior part proboscis b. Middle part collar c. Posterior part trunk

Trunk will grow quickly more than proboscis and collar.

In the pharynx gills are developed.

In the intestinal region hepatic caecae are developed.

Stomochord, Pygochord etc. will be developed.

Heart, blood vessels, and glonurukis are developed.

Coelom will be divided into 5 cavities.

From ectoderm nervous system is developed.

Thus slowly the tornaria will transform into adult. It will sink into the water. It will lead burrowing life.